Compass and course corrector.



No. 628,600. Patented July ll, I899.

J. M. FIELDS. COMPASS AND COURSE CORREGTOB.

(Application filed Apr. 1, 1898.) (N0 Model-3 2 Sheets-Sheet I.

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. 2 9 t 9 8 B m 7 s u y Q l e 7 u h S d 2 6 t n a t a P R 0 T C d Rm b .%1 D S 1 m D m s. w ER m. HwM .G m. M m a .Nm w J m m m .s P s A w P M 0 C 0 0 n 6 w m M N m UNITED STATES PATENT ()FFICE.

JOHN M. FIELDS, OF SAN FRANCISCO, CALIFORNIA;

COMPASS AND COURSE CORRECTOR.

SPECIFICATION forming part of Letters Patent No. 628,600, dated July 11, 1899.

' Application filed A rill, 1898. Serial No. 676,040. (No model.)

To all whom it may concern:

Be it known that I, JOHN M. FIELDS, a citizen of the United States, residing in the city and county ofSan Francisco, State of California, have invented an Improvement in Compass and Course Oorrectors and I hereby declare the following to be a full, clear, and exact description of the same.

My invention relates to a device which is especially designed for the correction of errors in the course of vessels, such as may arise either from the material of which the vessel is built, where iron or steel enter largely into it, or on account of the character of the cargo or from other causes.

It consists in details of construction, which will be more fully explained by reference to the accompanying drawings, in which- Figure l is a view illustratingthe apparatus as used with the arrow-dial. tical section of the same. Fig. 3 is a view showing the shadow-dial used in connection with a vertical pin. Fig. 4 is a section of the same.

This device is supported by the usual or well-known form of suspended ring or gimbal A, as shown in Figs. 1 and 2.

The outer circle B is graduated from zero to one hundred and eighty degrees on each side and has a variation-scale up to forty degrees on each side, so that the variation taken from the proper tables can be mechanically set at any time. p

The inner circle 0 has compass readings to quarter-points,and these readings are marked upon both sides of the dial, the zero-point upon one side corresponding with that of the outer circle, while the zero-point upon the opposite side is reversed, thenorth point or zero ofthe inner dial corresponding with the south or one hundred and eighty degrees of the outer circle, for a purpose to be hereinafter described.

The outer annular ring or dial has an interior sunken projecting rim orfiange which forms a seat, upon which theperiphery of the inner dial rests and is turuable, as shown at l), and the outer supporting-ring B, upon which the ring B rests, is similarly constructed to allow this ringto be turned and adjusted upon it.

Fig. 2 is a verfor the purposes of observation.

gives the necessary information without takin g an actual observation.

When the arrow and observation-dial are employed, the inner dial is so placed that its zero-point coincides with that of the outer one.

E is a central removable post, the lower end of which fits into a socket in the center, so that it may stand upright above the face of the dials. Transverse] y across the upper end is fitted a bar E, and this bar is connected with the top of the post E by a pivotjoint, (shown at E so that itmay be tilted to any desired angle about this pivot. At the ends of the bar E are the upright plates F and G, the plate F having a narrow vertical observation-slit made in it and the plate G having a vertical opening with a thread or wire 9 fixed in it in line with the slit in the plate F The bar E is preferably made tubular, and it also has a vertical thread in one end, the other end being open, so that if desired for night work it can be used for the observation of stars.

From the bottom of the post E an indexhand or arrow H extends over the dials and is fixed to the post, so as to be accurately and absolutely in line with the bar E and the sightplates F and G.

The operation of the device will thenbe as follows: The outer circle B is first set for the variation at the particular point on the earths surface where the vessel may be at the time of the observation, this variation being taken from the usual nautical tables, and is clamped, the variation east being to the right of zero and west to the left. An observation is then taken through the slit F across the vertical thread or wire G until they coincide with re lation to the sun, the arrow or index H moving with them, the ship being steadied on her course until the proper bearing is obtained.

This device will be used in connection with a compass and the magnetic and other bearings will be obtained by any of the methods employed by mariners and those skilled inthis art for obtaining such bearings. In fact, the operation of this device will be so readily understood by navigators that a detailed description of these old and well-known'operations is not believed to be necessary.

If it is desired to employ the shadow-pin and dial in place of the arrow and observation devices, the inner dial is reversed, with the lower side uppermost, and'a vertical pin or WireI is erected in line above the center of the dials. This pin may be an unsupported one of sufficient size and stiffness to maintain its erectness and have at the lower end a cylindrical enlargement, which is adapted to fit into a central socket, from which it can be removed at any time. I have preferred for the purpose of accuracy and to prevent injury to make this shadow-pin in the form of a wire stretched across an exterior rectangular frame I, having the socket-piece at the lower end centrally in line with the wire I and adapted to fit into the socket in the dial, as

' before described. When this pin is used, I

' sitions.

reverse the inner dial, so that the markings on this dial stand opposite to those of the outer one. In this case-the south point of the inner dial will be clamped with relation to the zero of the outer dial in setting it for variation. If the variation is to the east, it will be turned and clamped to the left of zero. If the variation is west, it will be turned and clamped to the right, thus reversing the po- The containing-box must set accurately in line with the ships keel. The variation is set on the outer dial, as previously described, and the suns true bearing is set on the ships head, and where the shadow of the pin falls on the inner dial will be the correct magnetic course the ship is making; If there is a difference between the compass reading and this line, that will be the deviation at that particular point and course. Now to set the course the variation is used as above and true bearing on the ships head. Then the helm is put to port or starboard until the shadow falls on the magnetic course it is wished to steer on the inner dial opposite the ships head, and the compass reading gives the course to steer to make the magnetic course good. If the true course is required, the outer circle will show it. To set the circle in north latitude, in the forenoon read from the south to the north round by the west and in the afternoon read from south to the north round by the east. In south latitude reverse the inner dial.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, isr 1. An apparatusfor correcting compass errors consisting of a suspended ring or structure, an outer ring fitting and adjustable therein having its surface graduated from zero to one hundred and eighty degrees each Way, a dial concentric with said outer ring, flanged and fitting therein with clamping devices, said dial being reversible and having compass readings upon opposite sides and reverse from each other, and a central socket-opening, a sight-bar upon one side of said dial and a shadow-pin adapted to be used upon the other side of said dial.

2. An apparatus for correcting compass errors consisting of a suspended ring or structure, an outer ring fitting and adjustable therein having its surface grad uated from zero to one hundred and eighty degrees each way, a dial concentric with said ring, flanged and fittingtherein with clamping-screws, said dial having compass readings upon opposite sides and reverse from each other, a central socketopening adapted to receive the standard of a sight-bar upon one side and the socket of a shadow-pin upon the other, said shadow-pin consisting of a rectangular open frame extending upwardly from the socket-piece and having a wire stretched vertically and centrally across the opening.

3. An apparatus for correcting compass errors, consisting of a suspended gimbal or ring and concentric inner and outer dials one of which has a surface graduated from zero to one hundred and eighty degrees and the other being reversible and having compass readings upon opposite sides and reverse from each other, the outer dial having a variationscale marked upon each side of the zero-point and the inner dial having a central socket or opening adapted to receive and support an observation-sight or a shadow-pin.-

at. In a device of the character described, the combination of a ring or circle having a surface graduated from zero to one hundred and eighty degrees each way, a dial concentric with the ring and capable of reversal, and having compass readings upon opposite sides and arranged one the reverse of the other, and means forsupporting observation devices and a shadow-pin so that the former may be used with the readings, upon one side of the dial and a shadow-pin may be used with the readings upon the opposite side of said dial.

In witness whereof I have hereunto set my hand.

' JOHN M. FIELDS.

WVitnesses:

S. H. NoURsE, .JEssIE O. BRODIE. 

